1. Technical Field of the Invention
The burning of small portions and hence granular firing products, such as wood pellets, wood chippings, small pieces of wood or dried maize proves to be economical and practical to handle. Large and bulky pieces of wood need not be transported and stored, and large logs of wood need not be fed to the fire. However, reducing the furnace capacity to a low value presents problems. If a suitable furnace is operated with a power of less than 1 kW using granular firing products, such as a wood pellet furnace, there is presently no suitable firing product feed device to reliably maintain such a weak fire continuously. In case of such low powers, the first difficulty is to keep the fire burning reliably. The second difficulty is to remove the ashes constantly and the third difficulty is to prevent the fire from reaching the feed flow of the firing product.
2. Description of the Prior Art
Conveyor screws already exist for wood pellet furnaces, which feed the fire with wood pellets continuously or only when needed. Additionally, these conveyor screws are also designed for much higher furnace capacities and it is possible to reduce the capacity to less than 1 kW using them by simply reducing the size of the conveyor screws or by reducing the rotational speed of the conveyor screws. Conventional conveyor screws are usually mounted at an oblique angle and function like an Archimedes screw. Moreover, the available pellet conveyor screws are not suitable for compact wood furnaces with small dimensions. Another problem that is observed is that when the pellets are fed slowly from the bottom into the fire, there is a danger of the fire slowly spreading down into the conveyor screw.